This project is concerned with the synaptic connections of the sensory root of the trigeminal nerve and the morphology of the neurons which comprise the main sensory and spinal trigeminal nuclei. These studies employ electron microscopy, the Golgi method and the use of tracer techniques which utilize the ability of neurons to pick up proteins (horseradish peroxidase) at their axon terminals and transport them back to their cell bodies. The objectives of these studies are to delineate trigeminal pain-temperature pathways and to broaden our understanding of oral-facial sensation.